1. Field of the Invention
The present invention relates to a receiver stage for a radio or a television receiver comprising a tuner, an intermediate frequency amplifier, a demodulator and a phase locked loop circuit.
2. Brief Description of the Background of the Invention Including Prior Art
Such receivers are provided with a tuner for selecting the different emitter frequencies of the radio and television station signals. These antenna signals fed to the tuner are transformed in the tuner by mixing with an oscillator frequency to an intermediate frequency. The intermediate frequency signals taken from the tuner are amplified in a following intermediate frequency amplifier. A demodulator following to the intermediate frequency amplifier demodulates the high frequency modulated signal to an audio frequency sound signal or respectively to a video frequency picture signal, which is fed to the final stages for reproduction in a loudspeaker or respectively on the screen of a television set. The individual electronic components such as tuner, intermediate frequency amplifier and demodulator have been conventionally disposed in separate component parts and were connected to each other via lines. These lines have to be shielded and are expensive for this reason. The required plug connections are susceptible to disturbances and form the sources of interferences, which can pass from the outside into the receiver station. Therefore, it has been taught to gather these named device units in a case. Thus there results an optimal shielding and the elimination of long connecting lines subject to the influence of disturbances (German Patent Laid Out DE-AS No. 1,958,993).
Receiver stations of more recent technology comprise capacitor diodes in the tuning circuits. The tuning voltage required for tuning is generated in this case with the aid of a phase locked loop circuit. This phase locked loop circuit provides a D.C. voltage, which results depending on a preselectable divider ratio of a frequency divider of the phase locked loop circuit. The phase locked loop circuit serving tuning purposes is disposed in a separate device component part. This arrangement with separation from the tuner unit however again results in the disadvantage, that interfering pulses can pass to the lines for the data input of the phase locked loop circuit as well as to the tuning voltage carrying line to the tuner unit, which can interfere with the tuning.